The present invention relates generally to disc drives. More particularly, the present invention relates to an improved actuator.
The actuator is in important sub-assembly in a disc drive, and any improvement in its performance leads directly to improvement in the performance of the disc drive. Actuators are moving parts that are designed to seek data at various locations on the discs by performing random seek motions at high velocities. Actuator parts are therefore subject to high frequency stimulation, causing them to vibrate and take time to settle over a track.
Ideally, actuators should have high stiffness so that the xe2x80x9csettlexe2x80x9d time is shorter. At the same time, a low inertia is desired so that the actuator can be moved quickly from one location to another with minimum power consumption.
To achieve the desired mechanical properties, the production of actuators has invariably involved many steps. For example, the U.S. Pat. No. 5,835,311, issued on Nov. 10, 1998 to Brooks, Jr. et al., for xe2x80x9cShock-Resistant Data Storage System Actuator Assemblyxe2x80x9d proposes an actuator arm that is fabricated from a metal. In order to achieve the desired stiffness which is critical to proper actuator performance, the actuator arm is further plated with another metal. Similarly, in the U.S. Pat. No. 5,627,701 issued on May 6, 1997, to Misso et al., for xe2x80x9cSkinned Foam Core E-Blockxe2x80x9d, the actuator is formed from a foam core material and subsequently coated with a non-porous stressed skin to provide the necessary mechanical properties.
In trying to reduce inertia, there have been attempts to use polymers to form the actuator. However, it is commonly recognized that non-metallic actuator arms poses additional assembly difficulties particularly to the swaging process which is the conventional method used for attaching the actuator arm to the suspension or the head gimbal assembly. Thus, although the U.S. Pat. No. 5,656,877 for xe2x80x9cSwing-Type Actuator and Method of Making Samexe2x80x9d, issued to Loubier on Aug. 12, 1997, proposes a thermoplastic for forming the housing of the actuator, it also proposes a metallic actuator arm. Similarly, the U.S. Pat. No. 5,654,849 issued to Hassibi et al. on Aug. 5, 1997, entitled xe2x80x9cMolded Swing-Type Actuator Assembly with Press-Fit Pivot and Spring-Loaded Ground Conductor Elementsxe2x80x9d. Assembly processes have to be incorporated into the production line for such cases, and even more so for those designs which have the various components separately molded and then built up to form the actuator. Examples of such built-up actuators are described in the U.S. Pat. No. 5,956,211 entitled xe2x80x9cChip attached to Actuator Arm having Heat Conducting Fibersxe2x80x9d issued Sep. 21, 1999, to Adley and in the U.S. Pat. No. 5,677,815 entitled xe2x80x9cSupport Arm for Use in an Actuator Assembly of a Digital Storage System with the Support Arm being Formed from a Polymer and including a Grounding Conductorxe2x80x9d issued Oct. 14, 1997, to Chan.
Because of the continuous pressure to reduce cost and simplify manufacturing processes, there is a need for an improved actuator which can be manufactured at lower cost and yet provide comparable or improved performance. The present invention provides a solution to the problems described above, as well as others, and offers other advantages over the prior art.
The present invention relates a lightweight actuator for use in a disc drive where the actuator body, yoke and actuator arms are molded as a single unit or as a unitary article. The actuator is molded from a polymer which is preferably a composite material chosen on the basis that its dynamic characteristics are comparable to the characteristics exhibited by conventional material. For example, the composite material may be chosen on the basis that the wave velocity in the composite material is roughly of the same order as that in aluminum. The resultant actuator is lighter and yet possesses equivalent or superior dynamic properties, as compared to conventional actuators. The present invention therefore provides for an improved actuator which can be produced through fewer manufacturing processes.
According to one embodiment of the invention, the actuator is molded with features at the actuator arms for coupling with one or more suspensions. Preferably, the features are configured for zero insertion force connection with the suspension. Thus, the present invention also allows for the application of improved connection methods at lower cost.